Many lighting applications make use of dimmers. Dimming may be achieved by means of standard control interfaces such as a digitally addressable lighting interface (DALI), a digital multiplex (DMX) interface or 0-10V dimming interface, or by line-side control methods such as leading-edge and trailing-edge dimming schemes and a power-line communication scheme. Although well established, each of these interfaces and schemes have limitations and undesirable characteristics.
For example, control interface standards such as DALI, DMX or 0-10V require installation of control lines in addition to power lines. Most existing lighting infrastructure, particularly outdoor lighting infrastructure, is designed for use with conventional lighting sources and does not support additional control wiring. Also, such control interfaces necessitate the use of a controller located either remotely or at every lighting source. Isolation and safety are concerns.
Line-side control methods alleviate the need of control lines. However, leading-edge dimming (triac dimming) or forward-phase dimming schemes chop a leading-edge portion of the voltage signal waveform, and trailing-edge dimming or reverse-phase dimming schemes chop trailing edge portions of the voltage signal waveform. Consequently, it is difficult to meet power factor and total harmonic distortion (THD) requirements with these dimming schemes. The dimming percentage is limited and the hardware necessary to implement these schemes is complicated. Power-line communication schemes add noise to the power line, resulting in transmission of electromagnetic interference on the power lines.
Thus, it would be desirable to provide a lighting driver and line-side dimming scheme that adjusts the dimming level of lighting sources without the use or installation of control wires and standard line-side dimming schemes, and that may be easily installed and implemented in existing lighting infrastructure.